I can remember as a yoof going to the airport for a post-booze coffee circa 1971 and wandering not only down the piers, but through the un-manned gates and out onto the apron under the parked aircraft!
Also, after the new terminal opened in the early 60s, there was just a small surface car park behind it - no multi-stories back then.
I can just about remember the old terminal, but usually we cycled up the wilmslow road to near where the barriers used to be that they closed for a 06 landing. I can clearly remember the piston-engined airliners taxying past on the other side of the fence after landing on 24.
Later, when I flew a based aircraft from the South Side, the only security was a guy in a hut at the Styal road south-side entrance - then you were on the airfield with acces to the hangars, aircraft, and runway. Doesn't seem that long ago, either.
SSD